RE: how many pins?
I had a 3 pin sight for a long time and just ran with that, but now that I've got into shooting a lot more and wanted to have pins available for practice shooting. I went with a 5 pin. 20, 30, 40, 50, 60 yards The 50 and 60 yard pins are purely for long range practice shooting. I would suggest going with a 5 pin for the reason above.
Good Luck.